1. Field of the Invention
The present invention relates to a coating apparatus for a traveling web, and more particularly to a coating apparatus which applies coating liquids to the traveling web such as polymer film, paper support, metal strip, etc.
2. Description of the Related Art
A roll coater, an extrusion coater, a slide bead coater, a gravure coater, a bar coater, etc. are known as a coater which coats a traveling web with a coating solution. These coaters are selected according to the coating solution and the product.
The Japanese Patent Application Laid-open No. 63-69573 discloses a coater in which two or more coating heads are arranged in series in the longitudinal direction of a traveling web, and the coating heads are used alternately. The U.S. Pat. No. 3,899,112 discloses a coater, which uses coating heads selectively on a web path composed of rollers.
However, in the case of the above-mentioned conventional coater, it is difficult to apply many types of the coating solution under a variety of conditions by one coater.
For example, the roll coater and the bar coater are suitable for applying the web with a thin layer; but when the web is already coated with something, a problem tends to occur that the coated layer is damaged.
In the case of the extrusion coater, the coated layer is hardly damaged. However, some coating solution causes a problem in that the web cannot be coated evenly or cannot be applied with a thin layer.
Furthermore, in a coater with only one coating head, there exists disadvantage that plenty of time is required before starting to coat a new solution which differs from previous coating solution, because it is necessary to clean the coating head and to prepare the new coating solution.
Therefore, in order to eliminate the above-mentioned disadvantages, two coating heads 1 and 2 are provided on the traveling path of the web 3 as shown in FIG. 13. For example, in the case when the coating head 2 is expected to be used by the method of the coating head 1, a web 3 is cut between a pass roller 4 and a pass roller 5, and the leading end of the web 3 is conveyed by being supported on a backup roller 7 via a pass roller 6, so that the coating head 2 can coat the web as shown in FIG. 14 (the Japanese Patent Application Laid-open No. 63-69573). However, this coater has a disadvantage in that it requires a lot of time for preparation because the web 3 should be cut every time the coating head is replaced, and the traveling path of the web 3 needs to be changed.
Moreover, the coating head may be provided in such a manner as to be installed and removed freely, and the coating head is selectively replaced according to the condition. However, the replacement of the coating head requires a lot of time, and it is difficult to install the coating head accurately.
The present invention has been developed under the above-described circumstances, and has its object the provision of a coating apparatus for a traveling web, which is able to coat the web with a coating solution efficiently without replacing a coating head or cutting the web.
In order to achieve the above-mentioned object, a coating apparatus for a traveling web comprises: plural coating heads arranged in a traveling path of the web; and traveling path changing means arranged close to the plural coating heads; wherein the traveling path changing means changes the traveling path of the web, so that the web is made close to at least one of the plural coating heads, which is used selectively for coating.
According to the present invention, the traveling path changing means arranged close to the plural coating head is moved to change the traveling path of the web, so that the web can become close to at least one of the plural coating heads, which is used selectively for coating. In the invention, there is no need to replace the coating head every time the coating conditions are changed. Moreover, there is no need to cut the web to change the traveling path of the web. Therefore, the web can be efficiently coated with the coating solution.
Furthermore, plural coating heads are provided in such a manner as to move toward and away from the traveling path of the web, and at least one coating head selected for coating is moved toward the traveling path of the web so as to be arranged close to the web, and another coating head is moved away from the traveling path of the web. Therefore, in the invention, the coating by the selected coating head can be performed without fail, and the incorrect coating by another coating head can be prevented.